Capacitor top plate over source/drain to form a 1t memory device

ABSTRACT

A method and structure for a memory device, such as a 1T-SRAM, having a capacitor top plate directly over a doped bottom plate region. An example device comprises the following. An isolation film formed as to surround an active area on a substrate. A gate dielectric and gate electrode formed over a portion of the active area. A source element and a drain element in the substrate adjacent to the gate electrode. The drain element is comprised of a drain region and a bottom plate region. The drain region is between the bottom plate region and the gate structure. A capacitor dielectric and a capacitor top plate are over at least portions of the bottom plate region.

BACKGROUND OF INVENTION

1) Field of the Invention

This invention relates generally to the structure and fabrication of a semiconductor device having a capacitor element and more particularly to a structure and method of forming a memory device, such as a 1T-SRAM.

2) Description of the Prior Art

As semiconductors having deep sub-micron features are fabricated, overall dimension of integrated circuit devices shrinks correspondingly. In the case of memory devices, overall dimension of each memory cell is also reduced. With the development of high tech electronic products (for example, computers, mobile phones, digital cameras or personal digital assistants), the amount of data that needs to be stored and process increases considerably. To meet the memory capacity demanded by these information technology products, smaller and higher quality integrated memory devices has to be developed.

Random access memory (RAM) is a type of volatile memory which has many applications in information technology products. In general, random access memory can be classified into static random access memory (SRAM) and dynamic random access memory (DRAM).

In each SRAM cell, digital data is stored as the conductive state of a transistor. Hence, a conventional SRAM cell consists of either a set of four transistors and two resistors (4T2R configuration) or a set of six transistors (6T configuration). On the other hand, digital data is stored as the charging state of a capacitor inside each DRAM cell. Accordingly, a conventional DRAM cell consists of a transistor and a capacitor (including a stacked capacitor or a deep trench capacitor).

In general, SRAM has a faster data processing speed and is possible to integrated with a complementary metal-oxide-semiconductor (CMOS) fabrication process. In other words, the process for manufacturing SRAM is simpler. However, one major drawback of incorporating SRAM is that area occupied by each cell is considerably larger (a SRAM cell with six transistors occupy an area roughly 10 to 16 times that of a DRAM cell). Yet, despite the considerable saving of area in incorporating DRAM cells, this advantage is counteracted by the complicated processes and hence the cost needed to manufacture the capacitor within each DRAM cell.

Recently, a one transistor SRAM cell (1T-SRAM) (also referred to as a pseudo-SRAM) has been developed. The 1T-SRAM uses a DRAM memory cell (1T1C configuration) to replace the SRAM cell (6T or 4T2R configuration) but is able to maintain the peripheral circuit structure of the original SRAM. Therefore, memory cell dimension is reduced and the level of integration is increased, and yet the refresh-free property and small random access cycle time of a SRAM cell can be retained. In other words, the 1T-SRAM is a potential candidate for replacing the conventional SRAM and DRAM cells.

FIG. 9 shows a schematic diagram of a 1T memory device.

Great advances have been made in the memory technology area. However, the prior art structures and methods can be improved upon.

SUMMARY OF THE INVENTION

The following presents a simplified summary in order to provide a basic understanding of some aspects of some example embodiments of the invention. This summary is not an extensive overview of the example embodiments or the invention. It is intended neither to identify key or critical elements of the invention nor to delineate the scope of the invention. Rather, the primary purpose of the summary is to present some example non-limiting concepts in a simplified form as a prelude to the more detailed description that is presented later.

An example embodiment of the present invention provide a structure and a method of manufacturing a memory device which is characterized as follows:

-   -   forming an isolation region surrounding an active region on         semiconductor substrate;     -   forming a first transistor over an first active region; the         first transistor comprised of gate structure, a source element,         and a drain element; the source element and drain element are         adjacent the gate structure; the source element and drain         element are doped with same conductivity type impurity;         -   the drain element is comprised of a drain region and a             bottom plate region; the drain region is adjacent to the             gate structure and the drain region is between the gate             structure and the bottom plate region;     -   forming a capacitor dielectric layer over the bottom plate         region and forming a top plate over the capacitor dielectric         layer; the top plate has top plate sidewalls;         -   whereby a memory device is comprised of the source element             that acts as a bitline, the bottom plate region that acts as             a bottom capacitor plate; the capacitor dielectric layer             that acts as a capacitor dielectric; the top plate that act             as a top capacitor plate.

An exemplary embodiment of a semiconductor device having a capacitance element is comprised of:

-   an isolation film surrounding an first active area on a substrate; -   a gate dielectric and gate electrode over a portion of the active     area; -   a source element and a drain element in the substrate adjacent to     the gate electrode; the drain element is comprised of a drain region     and a bottom plate region; the bottom plate region is adjacent to     the drain region and the isolation film; -   a capacitor dielectric and a capacitor top plate over at least the     bottom plate region; -   whereby a 1T memory device is comprised of the source element that     acts as a bitline, the gate electrode is connected to a word line;     the bottom plate region that acts as a bottom capacitor plate; the     capacitor dielectric layer that acts as a capacitor dielectric; the     top plate that act as a top capacitor plate.

The above and below advantages and features are of representative embodiments only, and are not exhaustive and/or exclusive. They are presented only to assist in understanding the invention. It should be understood that they are not representative of all the inventions defined by the claims, to be considered limitations on the invention as defined by the claims, or limitations on equivalents to the claims. For instance, some of these advantages may be mutually contradictory, in that they cannot be simultaneously present in a single embodiment. Similarly, some advantages are applicable to one aspect of the invention, and inapplicable to others. Furthermore, certain aspects of the claimed invention have not been discussed herein. However, no inference should be drawn regarding those discussed herein relative to those not discussed herein other than for purposes of space and reducing repetition. Thus, this summary of features and advantages should not be considered dispositive in determining equivalence. Additional features and advantages of the invention will become apparent in the following description, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of a semiconductor device according to the present invention and further details of a process of fabricating such a semiconductor device in accordance with the present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate similar or corresponding elements, regions and portions and in which:

FIGS. 1A, 1B, 2, 3, 4, 5, 6, 7A and 7B are cross sectional views for illustrating a structure and method for manufacturing a memory device according to an example embodiment of the present invention. FIGS. 1A-7B show example PFET devices.

FIG. 7C is a top down view illustrating a structure and method for manufacturing a memory device according to an example embodiment of the present invention.

FIG. 8A is a cross sectional view for illustrating a structure and method for manufacturing a memory device comprised of a NFET in a P-well as part of a two well CMOS approach according to an example embodiment of the present invention.

FIG. 8B is a cross sectional view for illustrating a structure and method for manufacturing a memory device comprised of a NFET in a P-well as part of a Triple well CMOS approach according to an example embodiment of the present invention.

FIG. 9 is a schematic diagram of a 1T memory device according to the prior art.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

The example embodiments provide a structure and method of forming a memory device such as a one transistor Static Random Access Memory (1T SRAM).

The example embodiments of the present invention will be described in detail with reference to the accompanying drawings. The figures may not be to scale.

Referring to FIG. 8A, an example completed memory device (e.g., 1T SRAM or DRAM) is shown. A point of the some example embodiments is that the (FIG. 7A) capacitor top plate 64 is over a doped bottom plate region 54B (a portion of the drain element 54A 54B).

Below an example SRAM is shown as a NFET. It should be understood that the embodiment is also applicable to NFET or/and PFET type devices. Also, both NFET and PFETs based 1T memory devices (e.g., SRAMs) can be formed concurrently on the same chip.

A. Form a FET on Active Region

Referring to FIG. 1A, we may form an isolation region(s) 30 surrounding an active region 31 on semiconductor substrate 10.

The active region 31 is near the surface where the FET will be formed is doped with a first conductivity type dopant, which for a PFET is n-type. In this example, a n-well 20 is formed.

The isolation regions can be shallow trench isolation (STI) regions comprised of oxide.

An example method of forming an example PMOS FET is as follows. Other configurations of the FET (e.g., logic transistors) are possible. The impurity types can be reversed to form a NFET using similar steps. Also, both PMOS and NMOS devices can be form concurrently.

We form a gate dielectric layer and a conductive gate layer over the substrate. The substrate can be a monocrystaline Si substrate or any suitable semiconductor substrate or structure. The gate dielectric layer can be comprised of any suitable dielectric such as silicon oxide. The conductive gate layer can be comprised of polysilicon, silicide and/or metals.

We pattern the gate dielectric layer and gate layer to form gate dielectric 34 and gate electrode 38.

We can implant p-type dopants to form LDD regions or source-drain extensions (SDE) 40 adjacent to the gate electrode 38. The SDE 40 can have a boron or any p type impurity. The SDE 40 can have a dopant concentration between 1E20 and 1E22 atoms/cc.

We can form gate spacers on the sidewalls of the gate electrode 38. The gate spacers can be comprised of one or more layers. In this example the first L spacer 42 can be comprised of oxide. The second spacer 44 can be comprised of nitride.

B. Form Source/Drain

Referring to FIG. 1B, next, we can implant p-type impurities into the substrate to form source element 50 and drain element 54A 54B. We can use the gate structure and the isolation regions are implant masks. If other devices are being formed on other areas of the substrate, a resist layer can be used to demark the appropriate areas for the implant. The source element and drain region are formed from the same conductivity type impurity. The source element 50 and drain element 54A 54B can be formed using the same implant step.

A feature of the embodiment is that the drain element is comprised of a bottom plate region that is extended or enlarged much more than a typical drain region.

The drain element 54A 54B may be comprised of two sections or regions:

-   -   (1) a drain region 54A that is adjacent to the gate electrode 38         and     -   (2) an bottom plate region 54B (extended drain region 54B) that         is between the drain region 54A and the isolation region 30.         The bottom plate region 54B (or extended drain region) will act         as the bottom plate of a subsequently formed capacitor.

The dopant profile of the extended drain region 54B (under the capacitor) is preferably substantially the same as the source 50 or drain region 54A.

The area of the extended drain region 54B is preferably about 2 to 100 times larger than the area of a conventional drain (or of drain region 54A which does not have a capacitor top plate formed thereover).

The source element 50, drain region 54A and extended drain region 54B can be formed from the same implant step.

The drain region 54A and a bottom plate region 54B preferably have substantially the same concentration and depth.

The source element 50, drain region 54A and extended drain region 54B can be have a B, BF2 or any suitable p type dopant, and may have a dopant concentration between about 1E20 and 1E22 atom/cc; and may have depth between 20 nm and 90 nm.

The implant process can comprise: implanting B ions at an energy between 5 keV and 30 keV at a dose between 1E14 and 5E15 atoms/square cm.

Compared to the drain region 54A, the area of plate region 54B can be between 200% and 10000% (2× and 100×) as large.

C. Form a Dielectric Layer and a Conductive Layer

Referring to FIG. 2, we can form a (capacitor) dielectric layer 60 and a conductive layer 64 over the substrate surface.

The dielectric layer 60 can be comprised of high-k dielectric (K>3), oxy-nitride or oxide and is preferably comprised of oxide. The dielectric layer can have a thickness between 10 and 500 angstroms.

The conductive layer 64 may be comprised of polysilicon, silicon, silicide and is preferably comprised of polysilicon. The conductive layer 64 can have a thickness between 500 and 2000 angstroms.

A conductive layer 64 comprised of polysilicon can be doped with (n or p type impurities depending on the type of FET being formed). For PMOS FET, the conductive layer 64 is preferably doped with p at a concentration between 1E20 and 5E22 atoms/cc.

For capacitor plate dopant concentration, normally the higher the concentration the better the conduction of the plate.

D. Form a Top Plate and Capacitor Dielectric Layer Over the Extended Drain Region

Referring to FIG. 3, we can pattern the conductive layer 64 and the dielectric layer 60 to form a top plate 64 and capacitor dielectric layer 60 over at least a portion of the extended drain region (bottom plate region) 54B. Preferably the top plate is over substantially all of the bottom plate region 54B. The top plate 64 has sidewalls.

Some remnants of the dielectric layer 60 may remain on the other surfaces. These remnants may be removed.

E. Form Top Plate Spacers

We can form top plate spacers 70A over the sidewalls of the top plate 64.

Referring to FIG. 4, we form a spacer layer 70 over the top plate 64 and sidewalls of the top plate. We can use a SPA process that is low temperature oxidation step.

The spacer layer can be comprised of oxide or nitride and is preferably comprised of oxide. The spacer layer may substantially consist of oxide or nitride and preferably of oxide.

Referring to FIG. 5, we etch the spacer layer 70 to form top plate spacers 70A on sidewalls of the top plate 64. The etch can remove the remnants of the dielectric layer that could remain of the other surfaces.

F. Form Silicide Regions

Referring to FIG. 6, we can form silicide regions 74A 74B 74C and 74D on the top plate 64, the drain region 74B, the source element 50 and the gate electrode 74C. The silicide regions may be: the top plate silicide 74A, drain region silicide 74B gate silicide 74C and source region silicide 74D. The silicide regions can be formed by depositing a suitable metal layer over the surface and annealing.

G. BEOL Processing

Referring to FIG. 7A, we may form an interlevel dielectric layer (ILD) 80 over the substrate. The ILD layer 80 can be comprised of oxide. We may form interconnects 82 84 thru the interlevel dielectric layer 80 to the devices. Additional levels of interconnects and dielectric layers may be formed. Additional process may be performed.

H. 1T Memory Device Components

FIG. 7B shows an electrical schematic overlaid on the embodiment's memory device (such as a SRAM).

A memory device (e.g., 1T SRAM) can be comprised of:

-   -   the source element 50 acts as a bitline,     -   the gate electrode 74C is connected to a word line (FIG. 7C-88);     -   the bottom plate 54B (e.g. extended drain) acts as a bottom         capacitor plate;     -   the drain region 54 a acts as the drain;     -   the capacitor dielectric layer 60 acts as a capacitor         dielectric;     -   the top plate 64 act as a top capacitor plate.

FIG. 7C shows a top down view of the device shown in FIGS. 7A and 7B. FIG. 7C shows word line 88.

I. Completed Memory Device

Referring to FIG. 8A, an example completed memory device (e.g., 1T SRAM) is shown. A point of the embodiment is that the (FIG. 7A) capacitor top plate 64 is over a portion of the drain element 54A 54B (e.g., bottom plate region 54B).

Some example embodiments with the top plate 64 over the extended drain 54B can have non-limiting features of:

-   -   the approach is self-aligned where the gate is self aligned to         the drain of the transistor     -   No additional implant step required to form the bottom plate         region     -   reduce the overall resistance in the circuit because of the         bottom plate region 54B is doped reduces the resistance     -   double poly approach (e.g., 38 and 64) allows the used of         deposition dielectric (i.e, high k materials)     -   Smaller dimension of embodiment's memory device (e.g., 1T SRAM)         thus greater packing density.     -   The embodiments memory device has a minimum spacing between the         Gate and the top plate because the drain region is connected to         the bottom plate region. (e.g., no undoped region between the         drain region 54A and the bottom plate region 56B.     -   Enables both p and N type 1T memory devices with double well         schemes

J. Double Well Embodiment

FIG. 8A shows an embodiment with NFET memory device (e.g. 1T SRAM) with a double well. For example, this NFET 1T SRAM (FIG. 8A) can be formed on the same chip with the PFET 1T SRAM (shown in FIG. 7A). Both PFET and NFET memory device can be formed simultaneously on the same chip.

For the NFET 1T SRAM in FIG. 8A, since the drain 154A is connected to the bottom plate 154B of the capacitor, the capacitor is isolated to the substrate by a PN junction. This prevents any leakages to the substrate. Allows formation of both P and N type 1T SRAM on same chip using double wells. Without the embodiment's PFET bottom plate (extended drain) 154B, a triple well would be required to prevent shorting of the capacitor to the substrate.

Example NFET concentrations ranges are listed in the table below.

Low conc High conc Region Low Atom/cc Atom/cc p-well 120 1E16 5E21 Drain 154A Bottom plate 1E18 5E22 region 154B (n-type) Source 150 (n-type) 1E18 5E22 TOP Plate 164 (doped with 1E20 5E22 N-typed dopant) FIG. 8A shows: gate 138, silicide regions 174A 174B 174C and 174C, ILD layer 180, contact 182, and interconnect 184

K. Triple Well CMOS Embodiment

FIG. 8B shows an embodiment of a NFET 1T SRAM in a triple well process. The NFET 1T SRAM can be formed on the same chip as the FIG. 7A PFET 1T SRAM. The thee wells could the be (1) Nwell 20(-FIG. 7A) (2) Pwell 120 (FIG. 8B), (3) 3^(rd) well (N3) 200 (FIG. 8B).

The third well 200 purpose is to further isolate the p-well 120 from the p-substrate 10. However, this triple well embodiment is not required to form both NFET and PFET 1T SRAMs. The second embodiment (FIGS. 7B and 8A) with the double wells can be used to form both NFET and PFET 1T SRAMs. Using the third well 200 is an optional aspect.

L. Non-Limiting Example Embodiments

The example embodiments of the invention can be used to make memory devices such as 1T SRAM's and 1T DRAMs. For a DRAM device, the area of the capacitor may need to be increased (compared to a SRAM) to increase the capacitance of the DRAM.

The example embodiment are not limited to the order of the steps shown.

Any element that is described as being able to be comprised of a material(s), may also consist essentially of that material(s).

In the above description numerous specific details are set forth such as, thicknesses, etc., in order to provide a more thorough understanding of the example embodiments of the present invention. Those skilled in the art will realize that power settings, residence times, gas flow rates are equipment specific and will vary from one brand of equipment to another. It will be obvious, however, to one skilled in the art that the present invention may be practiced without these details. In other instances, well known process have not been described in detail in order to not unnecessarily obscure the present invention.

Given the variety of embodiments of the present invention just described, the above description and illustrations show not be taken as limiting the scope of the present invention defined by the claims.

While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention. It is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures. 

1. A method of fabrication of a memory device comprising the steps of: providing an active region in a substrate; forming a gate structure over the active region; forming a source element, and a drain element adjacent to the gate structure in said active region; the drain element is comprised of a drain region and a bottom plate region; the drain region is adjacent to the gate structure; the drain region is between the gate structure and the bottom plate region; a first transistor is comprised of the gate structure, the source element and the drain element; forming a capacitor dielectric layer and a top plate over the bottom plate region; the top plate is over the capacitor dielectric layer.
 2. The method of claim 1 which further comprises: forming an isolation region that surrounds the active region; the top plate has top plate sidewalls; forming top plate spacers on the top plate sidewalls; forming silicide regions on the top plate, the drain region, the source element and the gate electrode; forming an interlevel dielectric layer over the substrate; forming interconnects through said interlevel dielectric layer to at least said source element, and drain region.
 3. The method of claim 1 wherein the capacitor dielectric layer and the top plate are formed by the steps of: forming a dielectric layer and a conductive layer over a substrate surface of said substrate; patterning said conductive layer and said dielectric layer to form the top plate and the capacitor dielectric layer over the bottom plate region; and whereby a memory device is comprised of the source element that acts as a bitline, the bottom plate region that acts as a bottom capacitor plate; the capacitor dielectric layer that acts as a capacitor dielectric; the top plate that act as a top capacitor plate.
 4. The method of claim 1 which further comprises forming a n type well in said active region; said first transistor is a PFET; and the source element and drain element are p type.
 5. The method of claim 1 which further comprises forming a P type well in said active region; said first transistor is a NFET; and the source element and drain element are n type.
 6. The method of claim 1 which further comprises forming a first p type well in said active region and forming an underlying second n type well under the first p type well; said first transistor is a NFET; and the source element and drain element are n type.
 7. The method of claim 1 wherein said source element, said drain region and said bottom plate region have a impurity concentration between 1E20 and 1E22 atom/cc; said source element, said drain region and said bottom plate region have substantially the same impurity concentration.
 8. The method of claim 1 wherein the area of the bottom plate region is between 2 and 100 times as large as the area of the drain region.
 9. A method of fabrication of a memory device comprising the steps of: providing a substrate having an active region in a substrate; the active region is doped with a first conductivity type dopant; forming a first transistor over said active region; said first transistor comprised of gate structure, a source element, and a drain element; the source element and drain element are adjacent the gate structure; the source element and drain element are formed from the same conductivity type impurity; the drain element is comprised of a drain region and an bottom plate region; the drain region is adjacent to the gate structure and the drain region is between the gate structure and the bottom plate region; forming a dielectric layer and a conductive layer over the substrate surface; patterning said conductive layer and said dielectric layer to form a top plate and a capacitor dielectric layer over the bottom plate region; the top plate has top plate sidewalls; forming top plate spacers on the top plate sidewalls; and forming silicide regions on the top plate, the drain region, the source element and the gate electrode.
 10. The method of claim 9 which further comprises forming an interlevel dielectric layer over the substrate; forming interconnects through said interlevel dielectric layer to said first transistor; whereby a 1T SRAM is comprised of the source element acts as a bitline, the gate electrode; the bottom plate region acts as a bottom capacitor plate; the capacitor dielectric layer acts as a capacitor dielectric; the top plate act as a top capacitor plate.
 11. The method of claim 9 wherein said conductive layer is comprised of a material selected from the group consisting of polysilicon, silicon, and silicide.
 12. The method of claim 9 which further comprises: forming a spacer layer over the substrate; and etching said spacer layer to form top plate spacers on sidewalls of said top plate.
 13. The method of claim 9 wherein said source element, said drain region and said bottom plate region have a impurity concentration between 1E20 and 1E22 atom/cc.
 14. The method of claim 9 wherein the area of the bottom plate region is between 2 and 100 times as large as the area of the drain region.
 15. A method of fabrication of a memory device comprising the steps of: providing an isolation region surrounding a first active region and a second active region on semiconductor substrate; said semiconductor substrate is doped with a p-type dopant; providing a n-well in said first active region and a p-well in said second active region; forming a first transistor over said first active region; the first transistor is a PFET; said first transistor comprised of a first gate structure, a first source element, and a first drain element; the first source element and first drain element are adjacent to the first gate structure in said first active region; the first source element and first drain element are formed in the same implant step and are doped with p-type impurities; the second source element and second drain element are formed in the same implant step and are doped with n-type impurities; the first drain element is comprised of a first drain region and a first bottom plate region; the first drain region is adjacent to the first gate structure and the first drain region is between the first gate structure and the first bottom plate region; forming a second transistor over an second active region; the second transistor is a NFET; said second transistor comprised of second gate structure, a second source element, and a second drain element; the second source element and second drain element are adjacent to the second gate structure in said second active region; the second source element and second drain element are formed from the same conductivity type impurity; the second drain element is comprised of a second drain region and an second bottom plate region; the second drain region is adjacent to the second gate structure and the second drain region is between the second gate structure and the second bottom plate region; forming a first capacitor dielectric layer over the first bottom plate region; and forming a first top plate over the first capacitor dielectric layer; the first top plate has first top plate sidewalls; forming a second capacitor dielectric layer over the second bottom plate region; and forming a second top plate over the second capacitor dielectric layer; the second top plate has second top plate sidewalls.
 16. The method of claim 15 which further includes forming a deep n-well under the p-well in the second active region.
 17. The method of claim 15 which further comprises forming top plate spacers on the first and second top plate sidewalls; forming silicide regions on the first and second top plates, the first and second drain regions, the first and second source elements and the first and second gate electrode; forming an interlevel dielectric layer over the substrate; forming interconnects through said interlevel dielectric layer to the memory device.
 18. A semiconductor device having a capacitance element comprising: a gate dielectric and gate electrode over a substrate; a source element and a drain element in said substrate adjacent to said gate electrode; the drain element is comprised of a drain region and a bottom plate region; the bottom plate region is adjacent to said drain region and said isolation film; a capacitor dielectric and a capacitor top plate over at least said bottom plate region. whereby a 1T memory device is comprised of the source element acts as a bitline, the gate electrode is connected to a word line; the bottom plate region acts as a bottom capacitor plate; the capacitor dielectric layer acts as a capacitor dielectric; the top plate act as a top capacitor plate.
 19. The semiconductor device of claim 18 wherein the source element, the drain region and a bottom plate region have substantially the same concentration and depth.
 20. The semiconductor device of claim 18 wherein the gate electrode and the capacitor top plate are formed from different conductive layers.
 21. The semiconductor device of claim 18 which further comprises capacitor spacers on the sidewalls of the capacitor top plate.
 22. The semiconductor device of claim 18 the area of the bottom plate region is between 2 and 100 times as large as the area of the drain region.
 23. The semiconductor device of claim 18 which further comprises a n type well in said substrate; and the source element and drain element are p type.
 24. The semiconductor device of claim 18 which further comprises a P type well in said substrate; and the source element and drain element are n type.
 25. The semiconductor device of claim 18 which further comprises a first n type well in said substrate and an underlying second N type well under the first n type well; said first transistor is a NFET; and the source element and drain element are n type.
 26. The semiconductor device of claim 18 wherein said source element, said drain region and said bottom plate region have a impurity concentration between 1E20 and 1E22 atom/cc; said source element, said drain region and said bottom plate region substantially the same impurity concentration.
 27. The semiconductor device of claim 18 wherein the area of the bottom plate region is between 2 and 100 times as large as the area of the drain region.
 28. The semiconductor device of claim 18 wherein the memory device is a 1T DRAM or 1T SRAM.
 29. A semiconductor device having a capacitance element comprised of: an isolation region surrounding a first active region and a second active region on a semiconductor substrate; said semiconductor substrate is doped with a p-type dopant; a n-well in said first active region and a p-well in said second active region; a first transistor over said first active region; the first transistor is a PFET; said first transistor is comprised of a first gate structure, a first source element, and a first drain element; the first source element and first drain element are adjacent the first gate structure; the first source element and first drain element are doped with p-type impurities; the second source element and second drain element are doped with n-type impurities; the first drain element is comprised of a first drain region and a first bottom plate region; the first drain region is adjacent to the first gate structure and the first drain region is between the first gate structure and the first bottom plate region; a second transistor over said second active region; the second transistor is a NFET; said second transistor is comprised of a second gate structure, a second source element, and a second drain element; the second source element and second drain element are adjacent the second gate structure; the second source element and second drain element are formed from the same conductivity type impurity; the second drain element is comprised of a second drain region and an second bottom plate region; the second drain region is adjacent to the second gate structure and the second drain region is between the second gate structure and the second bottom plate region; a first capacitor dielectric layer over the first bottom plate region and a second capacitor dielectric layer over the second bottom plate region; and a first top plate over the first capacitor dielectric layer and a second top plate over the second capacitor dielectric layer; the first top plate has first top plate sidewalls; the second top plate has second top plate sidewalls.
 30. The semiconductor device of claim 29 wherein the area of the first bottom plate region is between 2 and 100 times as large as the area of the first drain region; the area of the second bottom plate region is between 2 and 100 times as large as the area of the second drain region.
 31. The semiconductor device of claim 29 wherein said first source element, said first drain region and said first bottom plate region have an impurity concentration between 1E20 and 1E22 atom/cc; said first source element, said first drain region and said first bottom plate region substantially the same impurity concentration; said second source element, said second drain region and said second bottom plate region have a impurity concentration between 1E20 and 1E22 atom/cc; said second source element, said second drain region and said second bottom plate region substantially the same impurity concentration.
 32. The semiconductor device of claim 29 which further includes a deep n-well under the p-well in the second active region.
 33. The semiconductor device of claim 29 which further comprises top plate spacers on the first and second top plate sidewalls; silicide regions on the first and second top plates, the first and second drain regions, the first and second source elements and the first and second gate electrode; an interlevel dielectric layer over the substrate; interconnects through said interlevel dielectric layer to the memory device. 